As this type background-art technique, there is a hydraulic excavator forming a compact slewing device as disclosed in Patent Document 1. The hydraulic excavator has an undercarriage, an upper structure disposed on the undercarriage, a work device attached to the upper structure, and a cab, that is, an operator's cab, provided on the upper structure and having a door capable of opening and closing an opening surface forming a boarding port. The operator's cab has a left front pillar disposed on the work device side, that is, a front pillar, and a center pillar to which the door is attached rotatably, that is, a door mounting pillar. The front pillar and the door mounting pillar are provided to put the boarding port therebetween.
In addition, the door consists of two door pieces coupled with each other through a plurality of hinges in order to prevent the operator's cab from protruding outside the essentially requested turning radius of the upper structure which is not larger than the vehicle width in the hydraulic excavator forming a compact slewing device. The hinges are attached to edge portions of the respective door pieces provided vertically in a center portion of the whole door consisting of the two door pieces.
If the door were formed out of one door piece to increase the operator's cab, the turning radius of the upper structure would be beyond the aforementioned essentially requested turning radius which is not larger than the vehicle width. Thus, the slewing of the upper structure might be restricted by the work environment so as to cause troubles in various works performed by means of the work device of the hydraulic excavator forming the compact slewing device.